1. Field of the Invention
The present invention relates to a washing machine equipped with an apparatus of generating microbubbles of air in the detergent-containing water.
The process of generating microbubbles in the detergent-containing water for the washing machine has become widely employed as a cost-effective means for cleaning of laundry. The advantages of the washing machine with this process implemented therein comprise (a) that it reduces the amount of detergents to be added in the washer water introduced into the stationary tub of the washing machine; (b) that it prevents laundry in the rotating inner tub from being damaged or entangled; (c) that it requires shorter cleaning time and shows more thorough cleaning performance than the conventional washing machines devoid of means for generating microbubbles of air; and (d) that dry cleaning effect may be achieved even in wet cleaning together with this process so that sensitive laundry can successfully be taken care of.
2. Description of the Conventional Art
Key elements of the conventional bubble generating apparatus of the washing machines have been, so far, statically operating various gadgetries of microbubble generators such as the shear-generating turning elements or vanes developed by Federighi et al., U.S. Pat. No. 4,936,689; and the breaker of large bubbles into smaller ones as by Yoon et al., U.S. Pat. No. 5,167,798 even though its intended use is different from that for the washing machines. These gadgetries are, however, statically working devices playing a key role in generating bubbles in liquids inclusive of water. Other stationary devices such as the porous tubing, and various nozzles and orifices as developed by F. S. Gibbs, Inc., British Pat. No. 694,918 are to be cleaned up at a certain period of time interval to prevent foreign objects or object materials into which air bubbles are to be introduced from being stacked thereon to maintain the intended performance of the bubble generating means. Most of these stationary bubble generating devices have the potential of the problem of plugging because of the necessity for having finer pores or narrower passages of openings through which either the detergent-containing water or the air has to pass. If a choice of coarse porosity is made for the porous tubing or if nozzles having large openings are used to minimize the plugging problem, then the air bubble size will be too large to be useful for the washing machines.
Other problems with the conventional means for generating bubbles of air for the washing machine comprise (a) that washer water in the tub is hard to be circulated due to entrainment of fibrous or other foreeign object materials as developed from the laundry into the detergent-containing washer water circulated through these types of stationary bubble generating means, (b) that the bubble size cannot be made smaller than a certain critical value due to the fact that each of two mutually neighboring bubbles tend to get together to merge into a single bigger bubble with these stationary bubble generating means no matter how fast the flow of the detergent-containing water may be made, and that (c) as these conventional bubble generating apparatuses are basically in-line type devices and are disposed ahead of the detergent-containing water intake tube connected to the outer tub of the machine, number of bubbles in the detergent-containing water kept in the tub diminishes only due to absence of means for circulating the detergent-containing water in the stationary tub. Additionally, the shape of the bubble, that is the boundary between the detergent-containing water and the air, deviates much more from the true spherical one for large bubbles than for bubbles of smaller size. In other words, the rate of change in number of bubbles for larger bubbles is much higher than that of change for smaller bubbles for the same volumes of the detergent-containing water wherein microbubbles are introduced therein.
For these reasons set forth above, it is needed to have dynamically operating means for both generating microbubbles of air of smaller bubble size than that from the conventional statically working bubble generating means and keeping the rate of decrease in number of microbubbles generated as low as possible, uniformity in shape and size of the microbubbles generated in the detergent-containing water, and means for having therethrough circulation of the detergent-containing water in the tub of the machine with lessened plugging problems in order to keep a certain level of microbubbles contained in the detergent-containing water in the rotating inner tub of the machine.